Sharpening apparatus for forage harvester knives

Abstract

A forage harvester having an automatic grinding mechanism for the knives of the cutterhead, the grinding mechanism comprising a carriage carrying grinding means and being reciprocated back and forth across the cutterhead in the griding mode by endless drive means. The carriage is coupled to the endless drive means by a coupling member which is attached to the endless drive means chain and pivotally attached to the carriage. The coupling member is shaped and dimensioned such that the pivot axis of the connection to the carriage is substantially coaxial with the axis of rotation of each of the two sprockets which define the extent of the two runs of the endless drive means when the connection of the coupling member to the chain passes around that sprocket in moving from one run of the chain to the other. The drive means is provided with control means having means for commanding the termination of the grinding mode, and carriage-position-sensing means operable to deenergize the drive means at the end of the grinding mode such as to dispose the carriage in substantially the same home position at the end of each grinding mode irrespective of the position of the carriage at the instant of commanding termination of the grinding mode.

Having thus described the invention, what is claimed is: 
     
       1. In a forage harvester comprising: a rotatable cutterhead provided with a plurality of knives the tips of which describe the periphery of a cylinder when the cutterhead is rotated;   a grinding mechanism comprising a carriage carrying grinding means and being reciprocable, in a grinding mode, across the cutterhead with the grind means translating a line on said cylinder generally parallel to the axis of rotation of the cutterhead; and   drive means coupled to the carriage for effecting reciprocatory movement of the latter, the drive means comprising an endless member extending around at least two guide members arranged with their centers on a common line, generally parallel to the axis of rotation of the cutterhead;   the improvement comprising:   control means for said drive means including means for commanding the termination of the grinding mode and carriage-position-sensing means operable to deenergize the drive means at the end of the grinding mode so as to dispose the carriage in substantially the same home position at the end of each grinding mode irrespective of the position thereof at the instant of commanding termination of the grinding mode.   
     
     
       2. A forage harvester according to claim 1, wherein the carriage-position-sensing means comprises an electric switch which is so disposed as to be operable by the carriage each time the latter returns to the home position, and the command means comprises a timer, the arrangement being such that when the timer runs out, the carriage is not brought to rest until the position sensing switch has been actuated by the carriage next returning to the home position and thus being arrested in that position. 
     
     
       3. A forage harvester according to claim 2, wherein the drive means comprises an electric motor controlled by first relay contacts such that, when it is deenergized, it is connected on both sides to ground, whereby it is brought to rest substantially instantaneously so as to ensure that the home position of the carriage is always the same. 
     
     
       4. A forage harvester according to claim 1, wherein the home position of the carriage is disposed beyond an associated side wall of a housing for the cutterhead such that, when the carriage is in the home position, the grinding means is laterally spaced from the cylinder described by the tips of the knives when the cutterhead is rotated. 
     
     
       5. A forage harvester according to claim 2, wherein the command means and the position-sensing-means are connected in parallel, the position-sensing means normally passing electrical current and only being rendered open circuit when actuated by the carriage. 
     
     
       6. A forage harvester according to claim 1, wherein the grinding means is adjustably mounted in holding means which is movable with respect to the cutterhead to take up wear of the grinding means, and in that the control means further comprises means for detecting when the holding means is close to the cutterhead knife path and being operable to deenergize the drive means. 
     
     
       7. A forage harvester according to claim 6, wherein the detecting means comprises an electrical switch mounted on the machine in a position such that it is only actuatable by the holding means when the carriage is in the home position, whereby the carriage is always in that position when the drive means is deenergized by the detecting means.